Ab initio simulations of compressed liquid deuterium

Using ab initio molecular dynamics, we have investigated liquid deuterium under pressure, in a range of densities relevant to recent laser shock experiments. Our results show that between four- and sixfold compression, and temperatures between 5000 and 10 000 K, the liquid goes continuously from a dissociation/recombination regime, where a substantial proportion of atoms form D${}_2$ complexes, to a scattering regime, where mostly atoms are present. At about 10 000 K and sixfold compression, we find that the liquid is a poor metal. Our simulations point at a compression along the Hugoniot larger than indicated by old data, but smaller than predicted by laser shock experiments.